Rape investigation teams should be set up in every police force, a top policeman urged yesterday.

Scotland Yard Assistant Commissioner John Yates said specialist units are needed to improve the low conviction rate for rape and give expert support to victims.

Only 14 per cent of victims report the crime and more than 66 per cent of complaints do not make it to court.

The overall conviction rate for rape is just six per cent, which Mr Yates acknowledged is 'not good enough'.

He wants to see a team of specially trained officers in each force to deal with rape cases from start to finish.

Mr Yates, the Association of Chief Police Officers' spokesman on rape, said earlier this year that detectives are not always as professional when dealing with rape cases as with other serious crimes.

He criticised officers for treating complaints from victims with scepticism.

Yesterday he added: 'In recent years we have made significant advances in the way we approach investigation of this difficult offence, but despite that, delivery remains inconsistent and there is much more to do.

'But the fact that it's difficult means we need to redouble our efforts to ensure victims can have confidence in the way they are approached by those working in the criminal justice system.''

Challenged on BBC Radio 4's Today programme about the six per cent conviction rate , he said: 'It's not good enough. It is one of the most challenging cases and it's precisely because of that we believe, in ACPO, that specialist, experienced people, credible investigators who know these cases, know the pitfalls, should be dealing with them.'

The Met launched Project Sapphire - which has specialist rape teams in each London borough - in 2001 and has seen the conviction rate steadily rising. It is up 1.5 per cent since 2004 to 6.4 per cent.

Earlier this week, the Fawcett Society women's equality group complained that rape victims suffer a 'postcode lottery', with women in some areas five times less likely to see their attacker convicted than in others.